Dash 8 Q400 Severe Icing?

[BrummyGit]

I flew BHX -> FRA on Thursday morning with Flybe on a Dash 8.

About 10 minutes into the flight the aircraft start to become quite unstable as if we were entering turbulance, and there was a lot of vibration and shaking through the aircraft itself. At this point the engines were advanced to a high throttle setting and the pilot announced that were were experiencing "Severe Icing" and the engine speed had been increased for this reason.

Following the announcement I looked outisde and noticed that we were in quite dense cloud and that I could visibly see thick ice on the wings still increasing in thickness, but that the leading edges did seem to be gradually shedding pieces which I guess is due to the anti-icing boots expanding. I also noticed that the propellors where quite white, and that the centre of the propellor was very white as if covered with thick ice.

We continued on high engine revs for probably another 10 minutes and climbed to just above the clouds. Once out of the cloud the icing did stop and gradually clear along with the instability, although the vibration remained for a long time even after the engine revs reduced to normal. Some ice remained until we were on approach in Frankfurt by which time the vibration had also gone. I'm used to flying on the Dash 8 so I do realise that you always get some vibration, expecially sitting near the engines, but I was in row 2 and this was not "normal" from my experiences.

Knowing about previous Q400 icing incidents, I was just wondering how serious (if at all) this situation actually was as it was the first time I've experienced it as a regular SLF. It was quite concerning that the aircraft seemed to be icing up very quickly and I got the feeling that we were not in turbulent air, but rather the aircraft stability was a control issue?

[Lord Spandex Masher]

What may have felt like instability would just have been the props becoming slightly out of balance due to the ice. They are big props and any out of balance effect is quite large.

Increasing the propeller RPM, not engine, helps to shed the ice. Lucky you weren't sitting next to the props or you may have felt and heard large chunks of ice smacking against the side of the fuselage as they came off.

With deice boots on such turbo props it's necessary to allow some ice to build up before they are activated. So you will see ice building up on the leading edges before it's got rid of.

There are procedures to follow when encountering severe icing and also approach and landing with ice on the aircraft.

How serious was it? Well it appears to have been dealt with properly so not serious at all. IF the situation was allowed to develop further then it may have become a bit more serious...but it wasn't so that's ok!

[BrummyGit]

Thanks for taking the time to answer my questions.

I pretty much assumed that the situation had been dealt with correctly, and the vibrations certainly gave me the impression that the props were out of balance due to ice so that didn't concern me too much so long as they were still able to propell us forwards.

More surprising to me was the instability in flight - I am not trying to say that we were plummeting towards a school or hospital, but there was certainly enough movement to feel like turbulence. I repeat that I am not trying to imply that the crew were losing control, I was simply surprised that it seems something caused by the ice was enough to affect stability. I'm interested in what is the likely cause?

Also I guess we easily climbed above the problematic weather - albeit only a few feet above - but can the aircraft continue to fly safely through these conditions, or is it always a case of getting out of that situation asap?

Thanks again

[Sir Herbert Gussett]

Did the skipper actually say you were experiencing "severe icing"? I've always been told to never call anything "severe", or "very bad" etc as it doesn't give much hopes to the passengers!

[BrummyGit]

Yes I'm pretty much sure that the announcement was that we were "experiencing severe icing conditions" but as I was just assuming it was turbulence initially, there is a slim chance I might have misheard the announcement. It immediately got my attention and I looked out at the wing and engine on my side - there was thick and obvious ice for all to see.

It was a pretty strange flight really - just after we had climbed out of the icing, but while we were still experiencing high prop speed, instablity & vibration the PAX sitting directly in front of me passed out and needed oxygen from the cabin crew. They did a brilliant job :ok:

[Otto Throttle]

The only severe icing problem Flybe had was when some bright spark decided to remove it from the on-board sales trolleys to save some cash. :}

[BrummyGit]

The only severe icing problem Flybe had was when some bright spark decided to remove it from the on-board sales trolleys to save some cash. Tell me about it. I was surprised the PAX in front of me wasn't charged for the Oxygen they administered or the bottle of water they gave him when he came round.

[NWA SLF]

About 20 years ago I was on a 90 minute Fokker F-27 flight on which for the first 30 minutes or so it sounded like someone was on the outside of the plane beating it with a hammer - a very large hammer. Later when the air smoothed out and the noise went away the flight attendent came around serving drinks. I asked about the hammering, and he said he was curious himself as he had never heard anything like it. A bit later he came back, told me he had checked with the pilot. The noise was ice breaking off the props and beating against the fuselage. Until then I hadn't realized the skin has to be tough enough to withstand this beating. I made this flight twice a week for 2 years an never again experienced the ice hammer.

[Otto Throttle]

The fuselage skin itself isn't necessarily strong enough to withstand the beating from ice shedding from the props, so on the Dash 8 it is re-inforced with kevlar panels. Next time you look at the aircraft, you will see a patch that looks like a welded panel fixed onto the fuselage inside the props on each side. This is the kevlar protective layer, and on some aircraft you can even see the various dimples and small dents where ice has struck this panel over a period of time.

[FL370 Officeboy]

Knowing about previous Q400 icing incidents,

Which Q400 icing incidents would these be?